Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751819Ab1CQG0Q (ORCPT ); Thu, 17 Mar 2011 02:26:16 -0400 Received: from one.firstfloor.org ([213.235.205.2]:43013 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751440Ab1CQG0O (ORCPT ); Thu, 17 Mar 2011 02:26:14 -0400 Date: Thu, 17 Mar 2011 07:26:12 +0100 From: Andi Kleen To: Hidetoshi Seto Cc: Andi Kleen , Andrea Arcangeli , Andrew Morton , Huang Ying , Jin Dongming , linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/4] Check whether pages are poisoned before copying Message-ID: <20110317062612.GE11094@one.firstfloor.org> References: <4D817234.9070106@jp.fujitsu.com> <4D8172D7.3040201@jp.fujitsu.com> <20110317041424.GD11094@one.firstfloor.org> <4D819A2A.8050606@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4D819A2A.8050606@jp.fujitsu.com> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1226 Lines: 30 On Thu, Mar 17, 2011 at 02:20:42PM +0900, Hidetoshi Seto wrote: > (2011/03/17 13:14), Andi Kleen wrote: > > On Thu, Mar 17, 2011 at 11:32:55AM +0900, Hidetoshi Seto wrote: > >> So to avoid the above problem, add poison checks for both of 4K pages > >> and the THP before copying in __collapse_huge_page_copy(). > > > > I don't think you need the check for the huge page -- it should not be allocated > > in this case. > > Is there no case that the THP is once allocated but poison flag > is set before copy? Though I know it is one of corner cases, > having this check for THP is worse than nothing. There's a theoretical window, but it's only a few instructions. Probably not worth caring about, especially since you have a similar window after your check again. BTW normally I don't recommend to add new poison checks without doing new studies with page-types if the case is likely and happens with enough memory. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/